System for eliminating radio interference



April 23, 1935. J,-F. HEUBERGER 1,998,580

SYSTEM FOR ELIMINATING RADIO INTERFERENCE I Fi led Feb. 23, 1933 INVENTOR 52M 1w: ATTORNEY Patented Apr. 23, 1935 UNITED STATES SYSTEM FOR ELIMINATING RADIO INTERFERENCE Josef Friedrich Heuber assignor to Electrolux ger, Stockholm, Sweden, Corporation, Dover, Del.,

a corporation of Delaware Application February 23, 1933, Serial No. 658,032

In Germany 9 Claims.

This inventionmelates to a system for eliminating radio interference and more particularly to asystem for preventing the propagation of high frequency disturbances by dynamo electric 5 machines.

One object of the invention is to prevent electric motors of household appliances from interfering with radio reception.

Another object is to provide a protective means for portable household appliances such as vacuum cleaners, floor polishers, and the like.

A further object is to provide a simple, safe and a convenient device for the above purpose.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by referring to certain preferred embodiments thereof which are shown in the accompanying drawing for purposes of illustration only.

Of the drawing:

Fig. 1 is a diagrammatic representation of one embodiment of the invention, and

Figs. 2 to 7 inclusive are diagrammatic representations illustrating various modifications thereof.

Like reference characters denote like parts in the various figures.

In the following description and in the claims various details will be identified by specific names for convenience but they are intended to be as generic in their application as the state of the art will permit.

Referring to the drawing, l designates a housing which may consist of, for example, the housing of a household appliance such as a vacuum cleaner, floor polisher or the like. Located with-. in this housing and'electrically insulated therefrom is an electric motor having an armature l'l brushes l2 and field coils l3 which are shown, by way of example, as connected'in series relationship. The motor is connected to a line l by which current is supplied thereto. A suitable switch 25 may be included for controlling the operation of the motor.

An impedance, such as a pair of condensers I4, is connected across the brushes l2 of the motor and is enclosed in a metallic casing I! which is adapted to provide an electrostatic shield.

A second impedance, such as a condenser is, is connected across the line l5 and across the field coils l3. This condenser I6 is also enclosed in a suitable metallic casing l8 similar to the casing II. It is to be understood that casings l1 and I8 may be insulated from each other and March 7, 1932 are insulated from the housing III. For convenience, the condensers I which are connected across the brushes [2 will be hereinafter designated as brush condensers whereas the condenser l6 which is connected across the line l5 will be designated as the field or line condenser.

The condensers l4 and I6 are connected to casings l1 and I8 in various ways, as will be hereinafter described, either directly or through pro- .tective condensers, to form a protective circuit which is adapted toconstitute a high frequency by-pass, or a high frequency filter to prevent high frequency disturbances due, for example, to improper commutation or sparking atthe brushes, from being transmitted to the line or to the ex terior, and thereby interfering with radio reception.

In the form of the invention illustrated in Figure 1, thecondensers M are connected in series and the midpoint thereof is connected to the housing l8 of the line condenser I6.

Referring to the modifications of the invention illustrated in the other figures, Fig. 2 shows the mid-point of the brush condenser l4 connected to the casing I! which surrounds said condenser. In Figure 3 the casings I'! and I8 are interconnected and the brush condenser I4 is connected to the casing H. In Fig. 4, the casing 18 is grounded externally of housing I0 througha protective condenser l 9 and the brush condenser I4 is connected to said casing l8.

In the form illustrated in Figure 5, the brush condenser I4 is connected to the casing l8 through a protective condenser 28 and the line condenser I6 is formed in two sections which are interconnected, the mid-point being connected to the casing ll through a protective condenser 29.

In Figure 6, the casings I1 and I8 are interconnected, the brush condenser H is connected to the casing 11 through a protective condenser 30 and the line condenser I6 is connected to the casing l8 through a protective condenser 3|.

In the form of the invention illustrated in Figure 7, condensers l4 and I6 are both enclosed in a single metallic casing 20 to which the condenser ll is connected through a protective condenser 2|.

In the form of the invention illustrated in Figs. 4-7, it is to be understood that one or more of the protective condensers l9, 2| and 28 to 3| may be omitted and one or more of the casing connections in Figs. 5 and 6 may be omitted in instances where the disturbance is eliminated satisfactorily by the remaining connections as will be apparent to a person skilled in the art. Specific embodiments have been disclosed for purposes of illustration only. In any event the easings I! and I8 constitute electrostatic shields and the various condensers together with the casings El and i8, provide filter means for the purpose above specified.

It is to be noted that the housing Hi is electrically insulated from Ml parts of the motor circuit and that the protective condensers are grounded to separate casings which in themselves are electrically insulated from the housing id. This arrangement eliminates the danger of the operator coming in contact with the charged part-of the apparatus and receiving an electrical shock therefrom. The embodiments of Figs. l-3and 5-? also eliminate the necessity for a third wire connecting the apparatus to ground. This latter feature is of importance in connection with portable apparatus of the type above specified which would otherwise require a three wire cable and would require a special type of wall socket for grounding purposes.

The filter circuit may be installed as a unit, no part of which extends without the main housing and no part of which is exposed to accidental contact. Furthermore the device has been found particularly efficacious for the purpose specified.

While certain embodiments of the invention have been disclosed for purposes of illustration, it is to be understood that the invention is only to be limited in accordance with the following claims when interpreted in View of the prior art.

What -I claim is:

1. In combination with an electric motor adapted to form a part of a utility and having a commutating means and brushes associated therewith, a housing surrounding said motor and electrically insulated therefrom, means for preventing propagation of electrical disturbances comprising condenser means electrically interconnecting said brushes, and a metallic casing surrounding said condenser means, said casing being located within said housing and insulated therefrom, said condenser means being grounded to said casing.

2. In combination with an electric motor adapted to form a part of a utility and having commutating means, brushes, field windings and a current supply line, a housing surrounding said motor and electrically insulated therefrom, means for preventing propagation of electrical disturbances comprising condenser means electrically connected across said line, and a metallic casing surrounding said condenser means, said casing being located within said housing and insulated therefrom, said condenser means being grounded to said casing.

3. In combination with an electric motor adapted to form a part of a utility and having commutating means, brushes, field windings and a current supply line, a housing surrounding said motor and electrically insulated therefrom, means for preventing propagation of electrical disturbances comprising a condenser electrically interconnecting said brushes, a second condenser connected across said line and a separate casing surrounding each of said condensers and insulated from said housing, said condensers being grounded to said casings.

4. In combination with an electric motor adapted to form a part of a utility and having commutating means, brushes, field windings and a current supply line, a housing surrounding said motor and electrically insulated therefrom, means for preventing propagation of electrical disturbances comprising a condenser electrically interconnecting said brushes, a second condenser connected across said line and a separate casing surrounding each of said condensers and insu.

rebates lated from said housing, one of said condensers being grounded to one of said casings through a protective condenser.

5. In combination with an electric motor adapted to form a part of a utility and having commutating means, brushes, field windings and a current supply line, a housing surrounding said motor and electrically insulated therefrom, means for preventing propagation of electrical disturbances comprising a condenser electrically interconnecting said brushes, a second condenser connected across said line and a separate casing surrounding each of said condensers and insulated from said housing, said first condenser being connected to its casing.

6. In combination, a housing adapted to form a part of a utility, an electric motor mounted within said housing, said motor having a commutator, brushes and field windings and current supply connections, said motor being electrically insulated from said housing, a pair of condensers, a separate metallic casing enclosing each of said condensers, each casing being electrically insulated from said housing, one of said condensers being connected across the brushes of said motor, the other of said condensers being connected across said current supply connections and means grounding one of said condensers to one of said casings.

'7. In combination, a housing adapted to form a part of a utility, an electric motor mounted within said housing, said motor having a commutator, brushes, field windings and current supply connections, said motor being electrically insulated from said housing, a pair of condensers, a separate metallic casing enclosing each of said condensers, each casing being electrically insulated from said housing, one of said condensers being connected across the brushes of said motor, the other of said condensers being connected across said current supply connections and means grounding one of said condensers to one of said casings, and means grounding said last casing externally of said housing.

8. In combination, a housing adapted to form a part of a utility, an electric motor mounted within said housing, said motor having a commutator, brushes, field windings and current supply connections, said motor being electrically insulated from said housing, a pair of condensers, a separate metallic casing enclosing each of said condensers, each casing being electrically insulated from said housing, one of said condensers being connected across the brushes of said motor, the other of said condensers being connected across said current supply connections and means grounding one of said condensers to one of said casings and means grounding said last casing externally of said housing, said last means including a protective condenser.

9. In combination, a housing adapted to form a part of a utility, an electric motor mounted within said housing, said motor having a commutator, brushes associated therewith, field windings and current supply connections, said motor being electrically insulated from said housing, a pair of condensers, a metallic casing enclosing said condensers, said casing being electrically insulated from said housing, one of said condensers being connected across the brushes of said motor, the other of said condensers being connected across said current supply connections and means ounding one of said condensers to said casing.

J OSEF FRIEDRICH HEUBERGER. 

